Lubricating oil



Patented May 251943 LUBRICATING OIL Eugene Lieber, Linden, and Louis A. Mikeska,

Westfield, N. J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application April 7, 1939, Serial No. 266,532

17 Claims.

The present invention relates to lubricants containing hydrocarbons of mineral oil origin to which are admixed in relatively small proportions certain sulfur and related compounds which function mainly as oxidation and bearing corrosion inhibitors; and it also relates to the particular inhibitor compounds themselves.

The refined lubricating hydrocarbons derived from the more parafinic type of crudes and the simlar, but more extensively refined (to increase their parafiinicity) products from the mixed base type of crudes, are more susceptible to oxidation than the crude stocks from which they are prepared. In commercial usage, lubricating materials are subjected in thin films at elevated temperatures to the action of oxygen, and in the case of motor oils to the action also of the products of engine combustion. Under these conditions acidic substances are formed. These substances, especially in the oils, exert corrosive efl'ects upon the alloys of the cadmiumsilver, cadmium-nickel, copper-lead, high ('75 to 99%) lead type which are now employed as engine bearing material. Another result of service conditions is the formation in the oils of insoluble products which precipitate in the oil mass as sludge.

One proffered explanation of this breakdown oi highly refined lubricating oils is that natural inhibitors are present in the crude stocks and that such compounds are removed therefrom by extended refining. The-lubricating oil industry has endeavored therefore to counteract this instability of highly refined oils by the addition thereto of compounds having a reaction similar to, and frequently more eiiective than the natural inhibitors. The addition of these compounds to lubricating oil stocks is frequently unsatisfactory because improved stability in one respect is often coupled with a harmful efiect upon another property of the oil. Greases present similar problems.

A commercially satisfactory lubricating oil should be resistant to oxidation and the formation of corrosive compounds. It should also be tree of tendencies to deposit sludge and other solid material on engine parts and it should not cause ring sticking or gumming when employed in the engine. Satisfactory oxidation and corrosion inhibitors should possess the capacity in the lubricating oil of inhibiting oxidation and corrosion under the conditions of engine periormance without adversely aflecting-other prop- -erties of lubricants such as sludge formation,

hibitor compounds employed in the stabilized lubricants according to the present invention, satisfactorily overcome the susceptibilities of the unblended stocks to oxidation, and the corrosion of materials of the alloy type under the conditions of engine performance, and at the same time do not exert detrimental effects on the other desirable properties of a commercial lubricant.

The inhibitor materials employed in this invention are characterized by containing combined sulfur in xanthogen compounds and are represented by the general formula wherein R and R are organic radicals, X is oxygen, sulfur, selenium or tellurium, i. e. an element of the group of the negative elements of Group VI of the Periodic System, and Y is hydrogen, oxygen, sulfur, selenium or tellurium, and this element may be thefLs'ame as element X or it may be a difl'erentgione. This formula is purely diagrammatic and illustrative of a general attribute of the class of the compounds. The organic radicals R and R may be acyclic, cyclic, aromatic or hydroaromatic, or a combination of both in chemical structure. and heterocyclic radicals are suitable R and R groupings, but especially advantageous are those compounds in which R is an alkyl, aryl or alphyl (aryl-alkyl or alkylated aryl) radical and in which R is an alkyl or alphylradical.

Groups of compounds particularly suitable for use in this invention are the estersof xanthogen and thio-xanthogen carboxylic acids and the ethers corresponding to such esters. A general formula for the ester compounds of these acids is and for the ether type compounds is RXt]? S-RCHzXR wherein R denotes an alkyl, aryl or alphyl grouping R denotes an alkyl, cyclo alkyl or alphyl grouping, and X denotes oxygen, sulfur, selenium or tellurium. In these group formulae the alkyl grouping may be a wholly alkyl or a substituted alkyl grouping of normal or isostructure. The aryl grouping may be a phenyl, naphthyl, anthracyl or other condensed aromatic radical or any hyjdi-oxy, amine, alkyl or Alicyclic other substituent of these groupings. pounds of formula.

Com-

(2) Tertiary amyl phenyl ester of ethyl thioxanthogen acetic acid (3) Butyl ester of ethyl xanthogen acetic acid ll ll cimo CSCHr-C-O Cine (4) Butyl ester of ethyl thio-xanthogen acetic acid CaHsSPJSCHz-PI-OCJH (5) Ethyl ester of alpha ethyl xanthogen stearic acid H H C H: (CH2)15C H (S-C 0 Cans) C O C 2115 (6) Ethyl ester of alpha ethyl xanthogen phenyl stearic acid either l t cimornhomommcinhcms-uocnmcocnn or i ll CH3(CH2) CH(C HB)(CH1)0C]I(SUOCzHsXJOCzUs depending on whether the phenyl group is attached to carbon atom #9 or of the oleic acid employed in the preparation of phenyl stearic acid from oleic acid and benzene;

(7) Cresyl ester of ethyl xanthogen acetic acid ll oirno (medium-Q0113 (8) Cresyl ester of ethyl thio-xanthogen acetic acid II II onnscsomco-cm (9) Ethyl-xanthogen-ethyl butyl ether.

ll onnocswnm-o-mm The inhibitor compounds may be prepared by various processes. As an illustration, the preparation of a. phenyl ester of ethyl xanthogenacetic acid may be taken. The tertiary amyl phenyl-ester of ethyl xanthogen-acetic acid was obtained by treating 100 grams of potassium hydroxlde' in 500 .cc. of 95% ethyl alcohol with 136 grams of carbon disulfide, filtration from the reaction mixture of the potassium xanthogenate,

' for about an hour.

drying in air, andadding it to an aqueous solution of 132 grams of monochloro-acetic acid and 84 grams of sodium carbonate. This mixture was allowed to stand over-night at room temperature and then acidified with hydrochloric acid, extracted with ether, washed, dried and the ether evaporated off, leaving 240 grams of a relatively pure xanthogen acetic acid. 3'7 grams of this product was heated on a steam bath with 45.8 grams of phosphorus trichloride and then added to 20 grams of tertiary amyl phenol and located on a steam bath for 30 minutes. The product was poured into water, extracted with ether, washed and dried. On removal of the solvent, 26 grams of tertiary amyl phenyl ester of ethyl Xanthogenacetic acid was obtained as a light yellow liquid.

In the preparation of the tertiary amyl phenyl ester of thio-xanthogen acetic acid, ethyl mercaptan is used instead of the ethyl alcohol employed in the above preparation and it is advisable to employ benzene as an additional solvent medium in the reaction by which the thinxanthogen acetic acid is formed.

The ether xanthogen compounds are prepared by condensing ethylene chlorhydrins with alkylene xanthates or thio-xanthates.

An example of another general method for the preparation of these xanthogen compounds, the preparation of the cresyl ester of ethyl xanthogen acetic acid may be taken. Chloro-acetic acid was treated with cresol in the presence of sulfuric acid, as a catalyst, the product was dissolved in absolute ethyl alcohol, potassium xanthate was added to this solution and the mixture refluxed The reaction product was poured into water and upper oily layer so formed extracted with ether, washed and dried over sodium sulphate. The resultant solution was heated to remove the ether and then distilled,

giving a purified product boiling between C.

and C. at 3 mm. Hg. Other xanthogen compounds suitably prepared in similar manner were the normal butyl ester and the tertiary amyl phenyl ester, of ethyl xanthogen acetic acid, and the ethyl ester of alpha xanthogen stearic acid.

In addition to their use as oxidation and corrosion inhibitors in lubricating oils and greases, these compounds are also extreme pressure lubricants and addition agents in suitable proportions to base stocks to impart increased lubrication characteristics under severe operating conditions, The compounds may be employed quite generally as oxidation and corrosion inhibitors in the organic chemical industry in which products undergo deterioration due to oxidation upon exposure to air and oxidizing conditions. Illustrations of such uses are an admixture with fatty oils, soaps, synthetic resins, rubber and the like.

The oils used in the preparation of the stabil ized lubricants may be almost any type of lubricating oil distillate or residual stock. The oils used include highly refined stocks such as syn thetic oils, solvent extracted oils obtained by treatment of lubricating oil distillates with single solvents such as phenol, dichlorethyl ether, furfural, propane, nitrobenzene, etc., or multiple solvents such as propane-cresol, etc., clay or acid treated, also aluminum chloride treated oils hydrogenated oils and the like. The lubricating oils may also be light mineral oils, such as spindle oils and Oils generally used for textile treating, metal cutting oils, turbine oils, insulating and transformer oils, automobile and Diesel crankcase lubricants, steam cylinder oils and servable.

greases. The preferred compositions are, however, prepared by using a refined mineral oil having a viscosity of 50 Saybolt seconds up at 100 F. and up to 200 Saybolt seconds at 210 F.

The stabilizing materials are incorporated with the oil in any desired amounts depending on the conditions under which the lubricating compositions are to be used. When the conditions are severe it is desirable to add a relatively larger amount of the inhibitor compound than when the conditions are relatively mild. The inhibitor materials may be contained in the composite in concentrations ranging from .001% to In concentrations of about 5% or above extreme pressure lubrication characteristics are also ob- The preferred'inhibitor range, however, is from 0.05% to 0.3%.

The lubricants prepared according to this invention were subjected to the following tests:

OXIDATION RATE Trsr of a lubricating oil at elevated temperatures.

The results are generally given in the number of ccs. of oxygen absorbed by 10 cc. of an oil per 15 minute intervals at 200 C.

Com: Tssr This method is a means for determining the tendency of an oil to deposit solid matter upon heated metallic surfaces. It consists in slowly dropping the oil to be tested upon a heated metal (generally steel) cone, having a circumferential groove milled out in a screw fashion on the periphery so as to allow a time of contact of about one minute between the heated steel surface and the oil. A total volume of 60 cc. of oil is dropped from a dropping funnel during a period of 2 hours. The temperature of the cone may be any' Lean TOLERANCE Tss'r This test is used to determine the tendency of an oil to corrode bearings. It is also known as the Underwood Test. 1500 cc. of the oil is main tained at 325 F. and is sprayed for 5 hours upon two bearings of copper-lead and cadmium silver alloys respectively. The oil dripping from the bearing is re-circulated. The bearings are weighed before and after the test to determine any loss in weight. The test is then repeated with addition of a soluble lead compound, preferably lead oleate, the increments of 0.005% by weight of lead. A loss in weight of 50 mg. indicates the lead tolerance of the oil has been exceeded, and the amount of lead added in the previous test is recorded as the lead tolerance. A lead tolerance above 0.020 is generally considered satisfactory.

The following examples of lubricants made in accordance with the present invention will illustrate the composition and the action of the materials.

(ill)- Example I To a paraffinic type motor oil S. 'A. E. 20, was added amyl phenyl ester of ethyl xanthogen acetic acid in a concentration of 0.2%. Tests upon this blend gave the following data:

Cone de- Lead tol- 2 posit emnce Baseoil235. 0.45 0.005 Blitlldld oil as, 2!, 22, 31 o. 25 0.025

Example]! The butyl ester of ethyl xanthogen acetic acid in 0.2% concentration was added to the same base oil as in Example I. Tests upon the blend gave the following data:

Cone do: posit Lead tol- Eicample 111 The cresyl ester of ethyl xanthogen acetic acid in 0.2% concentration was added to the same base oil as in Example I. Tests upon the blend gave the following data:

. Cone de- Lead tol- Oudaiion rate posit Emma The present invention is not limited to any specific examples or theoretical explanations presented herein, such being intended solely for purposes of illustrations as modifications thereof within the scope of this invention will readily be apparent. It is our desire to claim all novelty in the invention disclosed herein.

We claim:

1. An improved lubricant comprising essentially a lubricant and a small quantity of a comin which R and R are organic radicals and X is a negative element of Group VI of the Periodic System.

3. An improved lubricant comprising essential- 1y a lubricant and a small quantity of a compound having the formula ly a lubricant and a small quantity of an ester of analkyl xanthogen acetic acid.

in which R and R are organic radicals.

8. An improved lubricant comprising essential- 1y a lubricant and a small quantity of an ester of an alkyl thlo-xanthogen acetic acid.

9. An improved lubricantcomprising essentially a lubricant and a small quantity of an aliphatic ester of an alkyl thio-xanthogen acetic acid in which the said aliphatic group contains from one to five carbon atoms.

10. An improved lubricant comprising essentially a lubricant and a small quantity of the normal butyl ester of ethylthio-xanthogen acetic acid.

11. An improved lubricant comprising essentially a lubricant and a small quantity of an aromatic ester of alkyl xanthogen acetic acid.

12. Animproved lubricant comprising essentially a lubricant and a small. quantity of the tertiary amyl phenyl ester of ethyl xanthogen acetic acid.

13. An improved lubricant comprising essentially a lubricant and a small quantity 01. a compound having the general formula in which R. and R are organic radicals and X is a negative element of Group VI of the Periodic System.

14. An improved lubricant comprising essentially a lubricant and a small quantity of a butyl ester of ethyl xanthogen acetic acid.

15. An improved lubricant comprising essentially a lubricant and a small quantity of a compound having the formula in which R, R and R" are aliphatic radicals. X is oxygen, sulfur, selenium or tellurlum, and Y is hydrogen, oxygen, sulfur, selenium, or tellurlum.

16. An improved lubricant comprising essentially a lubricant and a small quantity of an aliphatic ester of an alkyl xanthogen fatty acid in which the said aliphatic group contains from one to five carbon atoms. I

17. An improved lubricant comprising essentially a lubricant and a small quantity of an ester of a substituted stearic acid containing an alkyl-xanthogen radical s H R-OC-S where R is an alkyl radical.

EUGENE LIEBER. LOUIS A. MIKESKA. 

